Tubular core



March 2, 1943. s mc 2,312,587

Filed Dec. 29, 1941 Patented Mar. 2, 1943 UNITED STATES PATENT" OFFICE 3Claims.

This invention relates to tubular cores for use in casting concrete orcementitious material to provide passages in the cast product.

One object of the invention is the provision of a radially expansiblefluid tight tube for coring.

substantially circular passages in the casting of concrete or the like,the tube normally having a corrugated shape when deflated and assuming asubstantially circular shape when inflated.

Another object of the invention is the provision of a tube for coringpassages in concrete, the tube being so constructed as to expandradially when inflated and to disconnect or strip itself from the partlyset concrete as the tube isdeflated so that an effective strippingaction is initiated throughout the length of the cored passage at anumber of stripping zones having a predetermined radial spacing.

Another object of the invention is the provision of a radiallyexpansible fluid tight tubular core for making circular passages incasting concrete, the tube having a vulcanized rubber wall ofsubstantially corrugated form and provided with fabric or cords whichlimit the diameter of the tube when inflated and which maintain the tubeat substantially uniform length under varying internal pressureconditions.

Other objects and advantages of the invention will be apparent from thefollowing specification, the appended claims and the accompanyingdrawing In'the drawing,

Fig. 1 is a transverse section of a tubular core embodying the presentinvention;

Fig. 2 is a side elevation of a portion of the core, with a fragment ofouter rubber removed to disclose the fabric reinforcement; and

Fig. 3 is a perspective view showing the use of the tube in casting aconcrete beam.

The drawing shows a preferred embodiment of the invention as a radiallyexpansible pressure tight tubular core for use in making precastconcrete beams having one or more longitudinally extending circularpassages. Referring more particularly to the drawing, in which the samereference numerals have been used to designate like parts in the severalviews, I generally designates an elongated tube, of any desired length,and adapted to be subjected to internal pressure after being applied tothe form H in which the concrete or other cementitious material is to becast. In making precast concrete beams an elongated trough-like form, asshown in Fig. 3, may be employed, the end walls l2 of the form havingopenings l3 which correspond in diameter cored in the form. Thesepassages may be about 4 or 5 inches or more in diameter. -As shown in.Fig. 3 one of the core tubes i0 is in place, projecting through the endwalls [2 and inflated to the diameter of the openings, it beingunderstood that a second core tube is to be positioned in the adjacentopenings in the end walls before the concrete is poured into the form.

The tube I0 has a vulcanized rubber wall of substantial thickness. Thethickness of the wall of a flve inch diameter tube may be aboutthreeeighths of an inch and its hardness may be comparable to that usedin automobile tire construction. Fixed to and preferably embeddedbetween the inner and outer surfaces of the rubber wall is a fabricreinforcement I5 including fabric cords which extend continuously aroundthe axis of the tube and transversely of that axis. These annularlyextending cords are preferably interwoven with other longitudinallyextending cords reaching throughout the length of the tube. If desired,a series of spaced reinforcing wires or rods I! may be embedded in therubber walls. At their ends the tubes are closed by end portions I8 andI9, at least one of which is provided with a valve 20 through which airor liquid under pressure may be supplied to inflate the tube, andoperable to permit the release of the pressure fluid.

In its normal or deflated condition, the wall of the tube assumes asubstantially corrugated cross sectional form as indicated in Fig. 1,being vulcanized to that form in the process of its manufacture. Thefabric reinforcement l5 lies substantially parallel to the outer surfaceof the tube, following the corrugations of the tube walls. When the tubeis subjected to pressure, it expands radially, the inwardly extendingconvolutions being pressed outwardly, and as the pressure increases, theinwardly extending convolutions finally reach an expanded condition asindicated in dotted lines in Fig. l, in which the outer surface of thetube is substantially cylindrical and considerably larger in diameterthan a circle touching the convolutions of the deflated tube, since thecurvature of the inwardly extending convolutions of the deflated tube isconsiderably greater than the curvature of the expanded tube. Themaximum diameter of the inflated tube is limited, however, by the totalannular length of the fabric reinforcement, since the fabric cords,which are not capable of stretching any substantial distance, extendperpendicular to the direction of the tube axis. When the tube isinflated, therefore, in spite of any differences in rigidity or minordifferences in wall thickness throughout the length of the tube, theentire tube will have a substantially uniform diameter, thoseunsupported portions of the tube lying between the supporting end wallsI: having substantially the same diameter as the openings I! in whichthe end portions of the tube are located. The openings I; are madetocorrespond to the inflated tube diameter so that the tubes will beheld with sufliclent tightness to prevent any substantial loss ofconcrete through those openings.

The length of the tube remains substantially constant as the tube isinflated, since the longitudinally extending cords lying parallel to thetube axis prevent tube elongation, and the wires or rods ",1! those areemployed, also reinforce the tube against longitudinal expansion. "Afterthe concrete is partially set so that the cast concrete beam will retainits shape, the tubes Ill are deflated by opening the valves 20. Thewalls of the tube then return to their corrugated form, due to thetension created in the rubber, and the separation or stripping of therubber from the concrete initially takes place along radially spacedlongitudinally extending zones where the tension of the rubber isgreatest, namely at those points which will ultimately be returned toform the inner convolutions of the deflated tube. .As the pressureinside the tube is relieved, the separation of the rubber from theconcrete continues from these initial separation lines, the rubberstripping from the concrete in annular directions towards opposite sidesof the initial separation zones. By the time the deflation of the tubeis complete, the entire tube is free from holding engagement with theconcrete, and it may be readily withdrawn endwise from theconcretecasting and from the form in which the beam was cast. It is preferred,in making beams in the manner described, that the tube should bedeflated after the concrete is set sufllciently to maintain its shapebut before the concrete becomes so hard as to make an adheringconnection with the tube or core, but even though the tube is notdeflated at the most opportune time in the setting of the concrete, itwill separate itself when it is deflated, since a very large proportionof the contractive force of the tube is initially applied to theexpanded rubber walls at localized longitudinally extending zones tostart the stripping action, which then continues until the tube iscompletely separated from the concrete.

While the form of apparatus herein described constitutes apreferredembodiment ofthe invention, it is to be understood that theinvention is not limited to this precise form of apparatus, and thatchanges may be made therein without departing from the scope of theinvention which is defined in the appended claims.

What is claimed is:

1. -A radially expansible fluid tight tube for coring substantiallycircular passages in concrete, said tube having a vulcanized rubber wallof substantial thickness inherently assuming a corrugated crosssectional form when deflated and inflatable to assume a cross sectionalform which is substantially circular and of greater outside diameterthan a circle touching the outside of the convolutions of the deflatedtube, said wall having flexible reinforcing means imbedded therein andextending substantially transversely of the longitudinal axis of thetube normally in a corrugated path and limiting the diameter of the tubeby assuming a substantially circular path when the tube is inflated,said reinforcing means upon deflation of said tube causing initialseparation of said tube to begin in and progress from 'spaced areaslocated circumierentially thereof.

2. A radially expansible fluid tight tube for coring substantiallycircular passages in concrete, said tube having a vulcanized rubber wallof substantial thickness inherently assuming a corrugated crosssectional form when deflated and inflatable to assume a cross sectionalform which is substantially circular and of greater outside diameterthan a circle touching the outside of the convolutions of the deflatedtube, said wall having fabric reinforcement embedded therein and tendingto maintain said corrugations in the absence of fluid pressure, saidreinforcement including cords extending generally annularly transverselyof the longitudinal axis of the tube but in a normal corrugated path tolimit the outside expanded tube diameter and additional cords extendingaxially of the tube and maintaining the tube length substantiallyconstant under different internal pressureconditions, said reinforcementupon release of internal pressure developing a restoring force to returnsaid core to corrugated form.

3. A radially expansible fluid tight tube for coring substantiallycircular passages in concrete, said tube having a vulcanized rubber wallof substantial thickness inherently assuming a corrugated crosssectional form when deflated and inflatable to assume a cross sectionalform which is substantially circular and of greater outside diameterthan a circle touching the outside of the convolutions of the deflatedtube, said wall having flexible reinforcing means formed integrallytherewith and extending substantially transversely of the longitudinalaxis of the tube normally in a corrugated path and limiting the diameterof the tube by assuming a substantially circular path when the tube isinflated, said reinforcing means being under tension when the tube isinflated and developing a force when said tube is deflated for causingseparation of the tube from the formed passage initially in a series ofpoints spaced circumferentially around itsperiphery and corresponding tothe low points of the corrugations, and closure means at the ends of thetube, said closure means including avalve for supplying pressure fluidto the tube.

HARRY S. PRICE.

